William J. Altenhof – The University of Windsor, William D. Ames – K.S. Centoco Limited
In the present automotive industry, all corporations are focusing on developing automobiles which are light weight, fuel efficient, conform to a level of safety outlined by government regulations, and are available to the consumer at a reasonable cost. The automobile industry has placed a significant amount of time and research funding into developing vehicles which can meet these requirements. K.S. Centoco Ltd., a steering wheel manufacturer, located in Windsor, Ontario, Canada, has developed a testing machine to investigate collisions occurring with steering wheels. This machine considers several experimental parameters in impact testing while providing a large amount of information to be obtained in an experiment. Experimental testing was conducted on a four spoke steering wheel armature which is manufactured from a magnesium alloy. In an effort to compare the structural worthiness of magnesium and aluminum alloys in an impact situation, the identical armature was fabricated from a proprietary aluminum alloy and impact experiments were also conducted with the geometrically identical aluminum armature. Numerical simulation of the experimental process has also been conducted using LS-DYNA. Detailed four spoke steering wheel armature finite element models (employing both magnesium and aluminum alloys) have been developed and simulated under similar conditions which were conducted experimentally. Comparisons between experimental tests at six different impact situations with collisions between the steering wheel armature and a rigid plate are presented in this paper. As well, comparison of the finite element model is considered by investigating changes in the element formulation associated with the armature. The experimental and numerical observations indicate that the predictive capabilities of the aluminum material model are better developed than the magnesium material model. In addition, selection of the finite element formulation significantly affects the numerical results.
Yih-Yih Lin – Hewlett-Packard Company, Cing-Dao Kan – The George Washington University
For computer companies to design cost-effective machines for LSTC to optimize the software and for the LS-DYNA user to make an intelligent choice of machines, various factors that affect LS-DYNA’s performance must be investigated and understood. Therefore, we have embarked such an investigation with machines from both Hewlett- Packard and SGI. Many results are reported here. The factors considered include the following: memory systems, SMP vs. MPP LS-DYNA, single vs. double precision, cluster vs. ccNUMA configuration.
Romil Tanov, Ala Tabiei – University of Cincinnati
The present work concentrates on the development of correct representation of the transverse shear strains and stresses in Mindlin type displacement based shell finite elements. The formulation utilizes the robust standard first order shear deformation shell finite element for implementation of the proposed representation of the transverse shear stresses and strains. In this manner the need for the shear correction factor is eliminated. In addition, modification to any existing shell finite element for the correct representation of transverse shear quantities is minimal. Some modifications to correct Mindlin type elements are presented in the literature. These modifications correct the distribution of the transverse shear stresses only and use the constant transverse shear strains through the thickness. As compared to the above, the present formulation uses the correct distribution and is consistent for both transverse shear stresses as well as transverse shear strains.
Dr. Mark C. Anderson, Timothy K. Hasselman – ACTA Inc., John E. Crawford – Karagozian & Case Structural Engineers
With increasingly powerful computational resources at our disposal, it is becoming common- place to use analytical predictions in lieu of experimentation for characterization of physical systems and events. This trend, with its perceived potential for reducing costs, is the basis for the simulation-based procurement initiatives currently gaining momentum within the Gov- ernment and industry. However, a simulation-based approach is often sold to decision-makers via plausible visualizations of model simulation results; the simulations themselves having only been validated in an ad hoc manner using anecdotal comparisons with real events. Ex- perience has shown that, while simulation using physics-based models may lead to qualita- tively correct results, there can be large quantitative discrepancies between simulation and experimental results for a given physical event, and between simulation results from different analysts for the same event. Obviously, for simulation-based procurement to be a viable alter- native to more traditional test-based procurement, the quantitative accuracy of the simulations must be insured. To do this requires at least a modicum of experimental data (perhaps at the component or subsystem level) to serve as a yardstick with which the accuracy of simulation results can be measured. And it requires minimizing the differences between corresponding analytical and experimental results in physically meaningful ways, as well as characterizing the ability of the models to predict future events. This paper describes a toolbox for the vali- dation of nonlinear finite element models. The toolbox includes tools for quantitatively up- dating model parameters based on the differences between test results and analytical predic- tions, as well as estimating the predictive accuracy of the model based on generically similar comparisons. Use of the toolbox is illustrated for a DYNA model of a reinforced concrete wall subjected to blast loading.
Leonard E. Schwer – Schwer Engineering & Consulting Services, James M. Kennedy – KBS2, Inc.
Before performing safety assessments of spent fuel storage casks in drop and tipover accident simulations, method validation calculations are required. The validation process is outlined by the Nuclear Regulatory Commission (NRC) [Tang, et al., undated], and specifically requires the satisfactory replication of the steel billet drop tests, reported in NUREG/CR-6608 (UCRL-ID-129211) [Witte, et al., 1998]. In addition to reporting the test results in NUREG/CR-6608, Witte, et al. also provide simulations of the tests using the Lawrence Livermore National Laboratory explicit finite element code DYNA3D [Whirley, 1993]; several other organizations have used the Livermore Software and Technology Corporation code LS-DYNA [Hallquist, 1999]. Although other explicit finite element codes would also be applicable, the material model parameters provided for the concrete pad, upon which the billets are dropped, in NUREG/CR-6608 are specific for the Concrete/Geological Material, i.e. Material Type 16, in DYNA3D and LS-DYNA. This sole fact provides a great incentive for analysts to use DYNA3D or LS-DYNA. This manuscript briefly reviews the test configurations and results with recommendations on which configurations and results should be emphasized in comparisons with simulations. Next a brief review of the simulations presented in NUREG/CR-6608 with comments on the modeling and results and suggested improvements is provided. Then comments are provided on the utility of these results, both experimental and numerical, as a validation of the methodology with a particular emphasis on how they extrapolate to the cases of interest for spent fuel storage casks. Finally, a series of recommendations are included that should be considered, and discussed, by analysts providing simulations for spent fuel storage casks and the authorities requiring the safety assessment of these casks.
Ulrich Franz, Oliver Graf – CAD-FEM GmbH, Grafing/ Munich, Germany
Finite element side impact dummy models of the USSID and EUROSID are of major interest for industry, as more detailed models are required for better prediction capabilities, but still efficiency has to be maintained to some degree. Both type of models, the so-called FAT- USSID and FAT-EUROSID have been developed by CAD-FEM in cooperation with the German Association for Automotive Research (FAT). The main objective was to achieve highly validated finite element models. During the development process the models are vali- dated at three levels: material, component and assembly and tested finally by sled test appli- cations. Additional input was provided by other type of simulations from the LS-DYNA users within the FAT. This paper summarizes the experience gained during the validation and optimization process which may be used as a guideline for an efficient methodology to generate reliable finite element dummy models. Finally, the good performance of the current USSID and EUROSID models is presented for some selected tests.
Ramin Moshfegh, Xiangdong Li, Larsgunnar Nilsson, Ramin Moshfegh -Linköping Institute of Technology
Two mesh refinement indicators based on the gradients of effective stresses (GSIG) and effective plastic strains (GEPS), respectively, are proposed for adaptive finite element analysis of the large deformation, quasi-static or dynamic response of shell structures. The mesh refinement indicators are based on equi-distributing the variation of stresses or plastic strains over the elements of the mesh. A program module is developed and implemented in the nonlinear explicit finite element code LS-DYNA. This module provides element-wise refinement evaluations so that selective mesh refinements are carried out in regions of the mesh where the values of local indicators exceed a user-specified tolerance. The FE model of a conventional deep drawing process is used as numerical model, including both material and geometrical nonlinearities, in order to demonstrate the versatility of the two refinement indicators. Four different refinement indicators, based on angle change, thickness change, GSIG and GEPS based are applied in this investigation. To verify the numerical results against experiments, the anisotropic low carbon steel, FEP04, is used as a reference material. The numerical results are compared with experimental results regarding the thickness distribution versus cup height, effective plastic strain in the deformed sheet and punch force. It is shown that the new proposed indicators can identify finite elements, which have high gradients of stresses or strains so that the mesh is refined in the regions undergoing the most severe deformations and the numerical results are improved.
Ninig-an Hu, Ning-yan Zhu – SAE China (Society of Automotive Engineering of China)
It has been well applied in automotive manufacture of China about the technology of the numerical simulation of 3-D sheet metal forming processes during the recent years. Besides helping tool designers and artificers find optimal shapes of technical surface on the die, DYNAFORM is used in the early stages of the auto-body to work over the formability of various parts. In addition to the stamping process, the new forming technologies can be analyzed with DYNAFORM to find more efficient methods and optimal processing parameters for parts of the auto-body. The paper discussed how DYNAFORM is used to select a critical part in my plant and demonstrated how numerical simulation can reduce the developing time and costs of tools. For example, the formability analysis for the drawing die of the inside rear door on the car was performed using the numerical simulation of 3-D sheet metal forming processes. It is well known that the occurrences of both fracture and wrinkle were the two encountered difficulties in the stamping process. The numerical simulation was performed to analyze the metal-flow that caused the fracture and wrinkle on the draw-bead and it also acted to analyze the change of the blank’s outline that could bring up the fracture or wrinkle. The strain distributions were obtained from the numerical simulations and were also used in conjunction with the forming limit diagram to predict the onset of the fracture. The effect of blank-holder pressure and friction on the occurrence of the fracture and wrinkle was researched. To prevent the formation of the fracture and wrinkle, according to the above formability analysis of the numerical simulation, an optimum shape of the technical surface, the draw-bead distribution and sizes on the drawing die surface and the blank’s outline were finally determined.
Lars Olovsson – Livermore Software Technology Corporation, M’hamed Souli – Universite d’Artois
A new Eulerian-Lagrangian coupling algorithm and improved multi-material ALE- capabilities have made LS-DYNA an efficient tool for analyzing large deformation processes, such as bird strike events and forging operations. This paper contains two example problems that illustrate the current features of the code.
Clayton F. Heberling – Pressure Sciences, Inc.
Pressure Sciences Inc. used LS-DYNA to model a propane tank truck colliding with a concrete column. The analysis simulates an accident that occurred in 1994 in White Plains, New York. Correlation between the accident and an LS-DYNA analysis of that crash is described. The ultimate purpose of the analyses is to improve the crashworthiness of propane semi-trailers. To address the stiffening effect of the propane fluid, we correlated several models with drop tests that had been performed on 1/12 scale railroad tank car heads. The heads included unpressurized heads, fluid pressurized heads, and fluid pressurized heads with an air cushion. In order to model the liquid propane, explicit solid elements were used. The material model used for the propane was the elastic material model with the fluid option. The paper describes the procedure used to incorporate the elastic material model with the fluid option. The propane vapor was modeled using explicit solid elements and the null material model with a linear polynomial equation of state. The paper gives the derivation of a simplified version of the linear polynomial equation of state to simulate Boyle’s law. We were able to use LS-DYNA to obtain good correlations with drop tests when we modeled the liquid using the elastic material model with the fluid option and the vapor with a null material with the linear polynomial equation of state. We also obtained reasonable correlations between our LS-DYNA model and the White Plains, NY accident involving a propane tank truck and a concrete column.
Weilong Hu, Jeanne He – ETA-Engineering Technology Associates, Inc.
Basic behaviors of anisotropic properties of materials, relating to sheet metal forming processes, are discussed. The R-value is used to describe some forming problems including wrinkles and thinning failures. According to the analysis results, to point out that the anisotropic behaviors of materials affect the formability of blanks in some cases is very serious. Finally, a numerical example is presented to discuss this property further.
Gunasekar T. J., Mostafa Rashidy – EASi Engineering, Norman Ludtke – Ludtke and Associates, Bruce Spinney – NHTSA
A full vehicle finite element model of the 1995 Chevrolet Lumina validated in full frontal impact was used to simulate a frontal offset impact. The tibia index injury criteria set forth in the European Directive 96/79 were used to assess the injury indices of the occupant in frontal offset computer simulation. Based on the injury predictions from the baseline model, a structural modification to vehicle was made in order to reduce the tibia index. In the modified vehicle model simulation, the tibia index of the occupant was found to be reduced from 1.13 to 0.73 for the right tibia and from 0.62 to 0.45 for the left tibia.
Norman F. Knight – Veridian-MRJ, USA, Navin Jaunky – Eagle Aeronautics, USA, Robin E. Lawson – FDC/NYMA, USA, Damodar R. Ambur – NASA Langley Research Center, USA
Modeling and simulation requirements for uncontained engine debris impact on fuselage skins are described and assessed using the tied-nodes-with-failure (TNWF) approach and the element-erosion (EE) approach for penetration simulation. The TNWF approach is based on coincident nodes generated in selected regions of the target plate that are tied together using a constraint relation and the target plate is modeled with shell elements. The EE approach is based on eliminating or removing of an element once some criterion is reached.
Yinghong Peng, Zhaoyuan Wang, Xiongfei Yin, Xueyu Ruan – Shanghai Research Institute of Tool & Die
The kernel technology of a computer simulation system and the general procedure of dynamic simulation in sheet metal forming are presented. As an example, processing parameters of the experimental die of a car inner door panel were optimized with eta/DYNAFORM software. The appropriate round corner of punch, BHF and the correct layout of the drawbead were obtained.
Anthony P. Taylor – Irvin Aerospace Inc
The Beagle II Mars Lander is a portion of the European Space Agency (ESA) Mars Express program. Irvin Aerospace Limited, on contract to Martin Baker Aerospace Ltd., will provide the parachutes and airbags for the probe’s landing system. The purpose of the Beagle II Lander is to deliver scientific equipment, which will perform atmospheric and soil experiments focused on identifying signs of life on the Red Planet. To reduce development costs, the parachute system will be identical to the Huygens probe parachute, which is currently enroute to the Saturn moon Titan. This parachute has been the subject of previous papers. The parachute system, lander mass, and landing atmospheric conditions therefore define the conditions for the airbag first impact. This paper presents the results of concept development analysis for the Beagle II mission. Airbag design requirements, including the somewhat challenging impact velocity of 30.0 m/sec are presented. Several design iterations explored using the Explicit Finite Element Analysis (FEA) code LS-DYNA are presented.
Yvonne D. Murray – Aptek Inc
A computationally efficient wood material model is being developed and validated for performing LS-DYNA simulations of vehicle collisions into wooden guardrail posts. Typically, the failure modes and stress-strain relationships of wood depend on the direction of the load relative to the grain and the type of load (tension, compression, or shear). The model includes transversely isotropic constitutive equations and yield surfaces to simulate different stiffnesses and strengths parallel and perpendicular to the grain. Hardening and softening formulations simulate stress-strain relationships that are linear to brittle failure in tension and shear, and nonlinear and ductile in compression. A rate effects formulation increases strength with strain rate. For easy use, default material properties for Southern yellow pine and Douglas fir are provided as a function of moisture content, temperature, and grade. Correlations with static bending and bogie impact tests are being used to validate the model.
Raghu Echempati, Sarang Likhite – Kettering University
The aim of this paper is to discuss the educational issues concerning real and virtual simulation of sheet metals such as steel, magnesium and aluminum. Although expensive, aluminum and magnesium are being viewed as promising candidates in some of the automotive stamping applications. The philosophy explained in this paper deals with providing concurrent experience of real and virtual forming of sheet metals to engineers. There are several manufacturing processes like Casting, Molding, Metal Removal, Metal Forming, etc. Several different kinds of materials like metals and non-metals like plastics, ceramics and composites are considered to manufacture engineering products. Choice of a particular material depends on the type of application. One of the major challenges and goals in manufacturing is to see how to transfer several different ideas generated out of both experimental and theoretical research in to a state-of-the-art technology that can be applied to manufacture better quality products. Research, both in terms of better modeling of a manufacturing process and experimentation concerns with conducting parametric product and process design studies in order to produce near net shape (final shape) of a product. Computers no doubt are very helpful in advancing this research. Computer simulation of a manufacturing process can help in better visualization and understanding the different stages as a product is being shaped. Computer simulation deals with mimicking on a computer what it takes to do a prototyping of a product in the real world. While we learn to “think with hands” as we make prototypes and products, we learn to “think with the knowledge attained” as you perform simulation studies. It is very important to properly validate the results of a computer simulation with real experiments so that scientific tools can be eventually generated eliminating or reducing the need for making costlier and time consuming prototypes. Metal forming is divided in to bulk forming and sheet metal forming. Processes like rolling, forging, extrusion and drawing fall under bulk deformation, while bending, blanking, drawing, hole-expansion and stretching fall under sheet metal forming area. Kettering University in Flint, MI offers a sheet metal forming class (MfgE-404) based on understanding the principles behind formability of real sheet metals and a new virtual forming class (ME-510) based on simulating the real sheet metal process on a computer. Both classes need a basic understanding of manufacturing process and engineering materials. In addition, a good understanding of virtual forming requires a basic knowledge of solid modeling and finite element techniques. These two courses are unique to Kettering University. Kettering University is also very supportive of promoting undergraduate and graduate education and applied research in the real and virtual metal forming area. Many stamping industries promoted this idea of a combined real and virtual forming experience gained by engineering graduates. The mechanical and the manufacturing engineering departments are working together to achieve these goals. A NSF/CCLI proposal has been submitted last year (not funded). A revised proposal again is being prepared for submission to NSF. Recently, Kettering University funded a research initiation and improvement (RI/I) grant that deals with comparing the formability of sheets made of aluminum and magnesium with steel. Vegter, Pijlman and Huetink  in their paper discussed the deviations that occur due to experimental errors. Uniaxial tensile tests (ASTM E 646) were conducted on aluminum samples to predict inconsistencies in the strain state. Kuwabara and Bael  presented the experimental and analytical results of biaxial tensile tests to predict the yield locus of aluminum alloy 6XXX-T4. Kim, et al  discussed the analysis of wrinkling initiation and growth of aluminum A6114-T4 deep drawing process with controlled blank holding force. Bifurcation algorithm is introduced in the elastic-plastic finite element method. Several benchmark studies have been undertaken to predict punch force, thinning and several other characteristics of a deep drawn aluminum A6016-T4 cup . The results show a lot of inconsistencies between the different studies thus necessitating the proper understanding of the material behavior and the measurement techniques used for such studies.
Liang Xue, Zhongqin Lin, Zhengxu Jiang – Shanghai Jiao Tong University
Random geometric imperfections are natural in structures. The initial imperfections used to be ignored in structure strength analysis and thus geometric-perfect models were used in most case of numerical simulation. However, collapse of axially compressed square tubes is not such a case. LS-DYNA is used to simulate the effects initial geometrical imperfection has on square tube collapse. This study proves that dynamic progressive buckling of square box columns is sensitive to initial geometrical imperfections. The simulation results show that ideal square tubes tend to buckle in extensional mode, though is not likely to happen in experimental studies. Previous theoretical analysis suggests, that from the view of energy absorption extensional mode is a dynamic procedure of higher energy absorption characteristics than that of each of symmetric and asymmetric mode of square tube in case of high c/h. This phenomenon suggests that extensional mode is an unstable equilibrium that will easily change to another equilibrium – symmetric mode. In a real world, geometrical imperfection renders extensional mode almost unachievable for hollow square tubes. Three kinds of imperfections: deflection of wall, thickness deviation and length of section side unequal were discussed in this paper. The amplitude of imperfection was compared with the geometry tolerance. Numerical simulations are then performed using LS-DYNA. Compared with the experimental datum, deflection of wall is the main reason for the predominance of symmetric mode of axially impacted hollow square tubes. Several characteristic values with regard to the amplitude of wall deflection are discussed in particular. It is found that when the λcr , the initial impact force peak amplitude of deflection is less than a certain critical value value and the critical buckling load are almost the same and unchanged at a determined impact velocity. When deflection exceeds the critical value, buckling take place in elastic area and critical buckling force drops quickly. Energy absorbed before buckling also quickly drops to near zero when deflection is considerably large.
Yong Guo – Livermore Software Technology Corporation
An eight-node hexahedral solid element is incorporated into LS-DYNA to simulate thick shell structure. The element formulations are derived in a corotational coordinate system and the strain operator is calculated with a Taylor series expansion about the center of the element. Special treatments are made on the dilatational strain component and shear strain components to eliminate the volumetric and shear locking. The use of consistent tangential stiffness and geometric stiffness greatly improves the convergence rate in implicit analysis.
Xionghui Zhou, Ziqiang Liu, Zijie Zhang, Junyue Zhang – Shanghai Jiao Tong University
In this paper, the effect of drawbead on autobody panel forming and the theory of equivalent drawbead are discussed. Compared with the effect of real drawbead, the feasibility and essentiality of equivalent drawbead model in process optimization and finite element analysis of sheet forming are pointed out. An example of car inner door panel is presented. By means of eta/DYNAFORM software, a LS-DYNA based sheet metal forming simulation package, defects of the current process are found, and an optimized process is given.
Cing-Dao Kan – The George Washington University, Yih-Yih Lin – Hewlett-Packard Company
This paper reports the on-going evaluation of the current distributed memory (MPP) versions of LS-DYNA by using set of large size vehicle finite element models with number of elements ranging from 200,000 to 380,000. The evaluation focuses on the scaling performance, reliability, and consistency of the MPP code.
Thomas J. Vasko – Pratt & Whitney
Bird ingestion is a costly and difficult engine test to perform. It is also one of the most challenging and complex analytical investigations in engine design. The capability to model bird ingestion effects is, therefore, critical to the success of any competitive jet engine program. LS-DYNA has been used in the design and analysis of fan blades for bird-strikes. Descriptions of the bird and blade models used in the analyses along with the contact algorithms used to describe their interaction will be presented. In addition, comparisons of analysis and test results from bird-strikes on fan blades will also be presented.
Patricia P. Buso, James A. Sherwood, Julie Chen – University of Massachusetts-Lowell
The stamping of co-mingled glass/thermoplastic textiles for manufacturing relatively low- cost/high-volume structural composite automotive parts, e.g. truck beds and floor pans, is extremely attractive. These textile materials have yarns comprised of polymer fibers interwoven with the structural fibers, e.g. fiberglass. By heating the textiles in an oven, the polymer fibers melt and infuse the yarn, thereby removing the need to apply the resin in a separate step. The heated fabric can subsequently be stamped into a structural shape. The difficulty these fabric materials exhibit is that their deformation response exhibits both geometrical and materially nonlinear behaviors. The candidate material being evaluated in this study has a weave structure. The stamping mold for the current research is a hemispherical shape. Several samples of the candidate material were stamped to a variety of depths and over a range of temperatures to see how the sides of the material draw in as the part is being stamped. Splits on the hemispherical portion and wrinkles on the adjacent flat surface were observed. Several material models inherent to LS-DYNA were evaluated and a user-supplied subroutine was incorporated to consider the weave architecture. The correlation of the experimental and finite element results are presented.
Waldemar Z. Golinski, Richard Gentle – The Nottingham Trent University
Nowadays, people purchasing a new car are no longer simply looking for attractive styling, good performance and an efficient, reliable engine; one of their main concerns is now also the safety of the car. During the last decade, significant progress in improving car occupant safety has been made through the use of safety devices, such as airbags and advanced seat belts, as well as the construction of the car body itself. However, much still needs to be done to satisfy increasingly stringent legislation and public demand. This work deals with the problem of whiplash injuries that traditionally, due to difficulties in diagnosis, have been very difficult to investigate let alone prevent. Nevertheless, some progress has recently been made in this field. We have previously presented a simplified dynamic FE model of the cervical spine which, using comparisons with the latest experimental work on fresh cadavers, allowed the mechanism of injury to be defined. Subsequently the spine model was used in conjunction with a simple occupant model to investigate the possibility of creating a design tool for anti-whiplash devices. This work, although only preliminary, indicated that the approach of grafting a fully biomechanical FE model of the cervical spine onto a conventional FE model of a crash test dummy could produce an unrivalled analysis of a whiplash injury situation. In the present work a new, more advanced biomechanical FE model of the head–neck complex has been created and combined with the Hybrid III FE dummy model, which is the industry standard tool for occupant safety. The principal modifications are the method of modelling soft tissues and the representation of the inertial properties of the head to achieve a more realistic behaviour of the model.
Jason Wu – Motorola
The failure induced in radio/phone drop often associate with the damage of inside small components or its tiny substructures. The difficulty to detect the failure in drop simulation is: i) the right drop-induced shock at the components must come from the simulation at whole- phone model; ii) the required output at the small components needs very fine local mesh, which causes unbearable CPU cost and make the simulation impossible. Mass-scaling technique is unsuitable for the case. A global-and-local coupling method is presented in this paper to solve the problem. The method is demonstrated by an example of a connector (global model in coarse mesh) to search stresses of its solder joints (local model). The displacement and stresses calculated by the method are correlated to the results from a finely meshed model. The correlation verifies good agreement of calculated displacement in the two models, and small difference of stress prediction. The source of the error and possible improvement are analyzed in the paper.
Fuminori Oshita, Osamu Kunieda – The Japan Research Institute, Ltd. (JRI)
Nowadays, the CAE models are getting larger and more complicated. On the other hand, the simulation software including FEM codes, PRE-processors and POST-processors, must be quicker, more accurate and also easy to be used by various level customers. The authors introduce the developing high efficient and powerful design supporting system “DYNA-Works, completely specialized to LS-DYNA.” In this system, besides the general pre-post capabilities, the parts can be freely assembled into the simulation model. The response will be very quick even for the huge models. The data between PRE-POST systems and also among multi-stages problems will be connected seamlessly in this system. As a result, the total design cycle will be reduced very much.
W. Uddin, L. Ricalde – The University of Mississippi
Traditional static analysis procedures using linear elastic pavement properties may lead to incorrect structural response analysis of pavements. Many of these procedures do not appropriately consider the effects of dynamic loading and pavement nonlinearities such as joints and cracking. It is imperative to use appropriate and correct material properties for meaningful advanced computer simulations. This paper presents some results of traditional analysis and three dimensional-finite element simulations carried out on selected pavement- subgrade models of highway pavements. Results of static and dynamic analysis are presented using measured falling weight deflectometer (FWD) load pulses and deflections. Effects of viscoelastic material properties on pavement responses to dynamic FWD loading are investigated. A user defined material subroutine UMAT is described. The UMAT material routine incorporates a generalized Maxwell viscoelastic model and microcracking propagation methodology. The UMAT material routine is being implemented in the LS-DYNA code.
Ricardo F. Moraes, David W. Nicholson – University of Central Florida
Constitutive equations for a viscoplastic model with damage and thermal softening are implemented in the Finite Element (FE) code LS-DYNA using a User Defined Subroutine UMAT. A modified Johnson-Cook constitutive model, UMAT 15, which accounts for strain rate viscoplastic effects, is used. The Continuum Damage Mechanics (CDM) is based on Bonora formulation (Bonora, 1997). The combined material model, named UMAT 41, is added to the program static library using Digital Visual Fortran (FORTRAN 90). A brief procedure on how to implement a UMAT is also briefly discussed in this work. Using the User Defined Material, the solution of an explosive charge applied to a ring-stiffened welded structure is analyzed. This type of structure is widely used in ships and aircraft, which are subject to explosive or projectile attack. Results obtained using models with and without damage softening agree very well with previously published data with respect to crack paths. However, the time histories and thresholds are sensitive to the model used.
Bradley N. Maker, Xinhai Zhu – Livermore Software Technology Corporation
LS-DYNA has been widely used to study automotive crash. Default input parameters are generally chosen to give efficient, accurate crash simulation results. These defaults are not necessarily optimal for metal forming simulations. The following presents a standard procedure for conducting metal forming simulations with LS-DYNA. Recommended input parameters are identified in boldface type and included in boxed keyword input syntax for quick reference. A boldface zero value is entered for required input data which is model specific, such as the termination time term.
Bhavin Mehta, Shr-Hung Chen, Srikanth Patlu, Prasad N. Petkar, Robert L. Williams – Ohio University, Lee P. Bindeman – LSTC, James M. Kennedy – KBS2 Inc., Joseph Pellettiere – Wright-Patterson Air Force Base
This paper describes the Integration of ATB (Articulated Total Body), a rigid body dynamics program and LS-DYNA, a finite element analysis program for PC-based occupant/seat restraint modeling. The integration of ATB and LS-DYNA provides a single simulation tool with the advantages of each individual code. The results of several cases and validation are also described in detail. The output of the coupled software is found to be consistent with the output from the already validated ATB program.
Masaki Shiraishi, Hiroshi Yoshinaga, Naoaki Iwasaki, Sumitomo Rubber Industries – LTD, Kimihiro Hayashi – The Japan Research Institute,Ltd
In recent years, CAE (Computer Aided Engineering) has become very popular for effective development of many industrial products. In the development of automobile, CAE has been applied in many fields. About endurance and fatigue analyses of automobile, it is necessary to simulate the force by road input, and accurate tire model is necessary for this. But the construction of tire is very complicated and its model is so complicated that large calculation resource is necessary. Such a simulation is not useful for actual automobile development. Then we tried making simplified tire simulation model that express the tire properties of minimum requirement. After developing tire model, we applied the model to curb striking simulation to confirm the availability of the model.
Brian Wainscott, Jason Wang – Livermore Software Technology Corporation
The emergence of distributed memory and cluster based computers is a recognized trend, with obvious cost/performance benefits. Here we discuss strategies for efficient utilization of these architectures on industrial problems. Results are presented which investigate the communication bandwidth and latency requirements for production environments.
Ala Tabiei, Quing Chen – University of Cincinnati
A micro-mechanical model is developed for laminated composite materials and implemented in the explicit finite element method. The objective of this study is to get an accurate and simple micro-model, which can be used in the displacement-based nonlinear explicit finite element code DYNA3D. The micro-mechanical model implemented in the explicit finite element code can be used for simulating the behavior of composite structures under various loads such as impact and crash. The stress-strain relation for the micro-model is derived for shell element. Micro Failure Criterion (MFC) is presented for each material constituent and failure mode. The implemented model is validated through several test examples. As a demonstration case of the stability of the developed micro-model a finite element model of Graphite/Epoxy tube structure is developed and simulated under axial crash.
Romil Tanov, Ala Tabiei – University of Cincinnati
A new homogenization procedure for Finite Element (FE) analysis of sandwich shells was recently developed and presented by the authors. To the authors’ knowledge all present FE approaches to sandwich structures are incorporated into the FE formulation on the element formulation level. Unlike other formulations the present approach works on the constitutive level. A homogenization of the sandwich shell is performed at each call of the corresponding constitutive subroutine. Thus the sandwich nature of the problem is hidden from the main FE program. As a consequence there is no need to develop a new shell element formulation, but instead all available homogeneous shell elements in the utilized FE code can be used for the analysis of sandwich shells. This would provide versatility of the FE analysis and potentials to trade off between the level of accuracy and computational efficiency by using more accurate or simpler shell elements. Furthermore, the sandwich homogenization procedure (SHOP) can be easily coupled with a composite homogenization model to enable analysis of sandwich shells with composite faces. To validate the present approach and check its accuracy, efficiency and overall performance it is implemented in a finite element package and combined with existing first order shear deformable shell elements for homogeneous materials. Results are obtained and herein presented for problems previously investigated experimentally and by different theoretical and numerical techniques. The presented results show good agreement with published results from far more complicated and computationally intensive analyses, which builds confidence in the approach and motives its future elaboration and development.
Ala Tabiei, Romil Tanov – University of Cincinnati
This work presents the finite element formulation of a higher order shear deformation shell element for nonlinear dynamic analysis with explicit time integration scheme. A corotational approach is combined with the velocity strain equations of a general third order theory in the formulation of a four- noded quadrilateral element with selectively reduced integration. A bilinear isoparametric formulation is utilized in the shell plane resulting in 9 degrees of freedom per node. The formulation requires C0 continuity for the nodal variables. The finite element implementation of the new element in a general explicit finite element code is described in details, including boundary conditions and nodal mass calculation. A simple formula for the explicit time integration critical time step of the higher order element is developed. The described element is capable of correctly representing the through thickness distribution of the transverse shear, which makes it suitable for composite and sandwich shells analysis. In addition, the developed shell can be used for better representation of plastic flow through thickness in isotropic materials. It has been added to the element library of the nonlinear explicit finite element code DYNA3D. Its performance has been evaluated through a series of standard shell verification test problems, which show great promise for many applications. The results are presented in Part II of the present work.
Ala Tabiei, Romil Tanov – University of Cincinnati
This work presents the results from a set of verification shell problems used to assess the performance of the higher order shear deformation shell elements formulated in part I of the present study. The developed element has been added to the element library of the nonlinear dynamic explicit finite element code DYNA3D. Several standard verification test problems are performed using the code DYNA3D with the developed shell element. Results are presented for different test problems and are compared with experiments and results from other existing shell elements. The good overall performance builds confidence in the formulation and implementation of the proposed higher order shear deformable element. The superior advantage of the developed element is evident in one of the examples presented for representation of plastic flow through the thickness in isotropic materials. The element can be used in crash and metal forming simulations in local areas of high transverse shear stresses. Local areas of crack in crash applications and splitting in metal forming applications can be modeled more accurately with the developed shell element. Key words: nonlinear higher order shear deformation shell elements, explicit finite element analysis, shell verification test problems, shell element performance
Lou Pingyi, Cao Deqing – Beijing Engineering Software Technology Co. Ltd.
Copper water stop is used to prevent water seeping through the dam. To get the stress and strain distribution status of water stop, LS-DYNA was used to make a nonlinear analysis. Experiment results and simulation data were tested to be consistent.
Karl Schweizerhof – CAD-FEM GmbH, T. Münz, O. Graf, M. Walz – CAD-FEM GmbH, Chen Tsay, J. O. Hallquist – Livermore Software Technology Corporation
Adaptive strategies are nowadays applied in a rather standard fashion in linear static analyses where reliable global and local estimators are available for many problems ,,. Con- siderable progress has been achieved for nonlinear problems , , also in- volving contact , because fairly reliable estimators exist, resulting in efficient procedures. However, for transient loading only limited success has been achieved so far ,,,. This is due to the fact that inertia effects and time integration schemes introduce additional complexity and approximations. As a result, no reliable error estimation is yet possible for large deformation dynamic problems such as metalforming and crashwor- thiness analyses. Adding to the difficulties is the complexity of the structures to be analyzed. Crashworthiness models violate, at least in parts, the continuum mechanics approximations such as multiple shell connections, spotwelds or shell-beam connections. Although proposals for the adaptive static analysis of composite shell connections exist , these cannot easily be applied to dynamic problems. In particular, the a-priori definition/detection of such non- continuous parts is a difficult task and contact regions need high resolution to achieve reason- able error estimation. Furthermore, there is no reliable error estimation possible for the very efficient and simplified shell elements with reduced integration and hourglass control – the “work-horse” in crashworthiness analysis. Nevertheless, some standard error indicators have been implemented and tested for some large deformation problems in LS-DYNA with some success . As a consequence, for very general, large scale crash models in industrial practice currently only adaptive procedures remain which use error indicators based on simple ideas such as geometrical relative deformations . These methods have to be combined with adaptive meshing schemes which allow only a certain level of refinement due to efficiency reasons. Additionally, the refinement has to be restricted to various points in time. In particular for deep drawing applications, it often appears to be very beneficial to step back in time and re- start the analysis with an adapted mesh at a previous point in time. LS-DYNA  has been recently enhanced by the capability to allow adaptive schemes for certain type of shell connections. In addition, it was observed that it is very effective to refine the mesh in metalforming applications prior to contact with small radii. The introductions of these so-called look-ahead algorithms limit the number of back-steps in time to almost zero. This contribution highlights these new features in LS-DYNA. The numerical examples range from metalforming analysis, simple buckling analysis of a structural member to a complex crashworthiness model. The merits and the limits of the currently available methods in LS- DYNA are illustrated. This may lead to further insight on how future efficient error estimators could be developed on a sound mathematical basis, even for large deformation problems with high complexity. Some hints are given to use the implemented indicator and the adaptive meshing efficiently improving the quality of the analyses.
Nielen Stander – Livermore Software Technology Corporation,Livermore, CA, Rudolf Reichert, Thomas Frank – DaimlerChrysler, Stuttgart, Germany
This paper focuses on a successive response surface method for the optimiza- tion of problems in nonlinear dynamics. The response surfaces are built using linear mid-range approximations. To assure convergence, the method employs two dynamic parameters to adjust the move limits. These are determined by the proximity of successive optimal points and the degree of oscillation, respective- ly. Three diverse examples namely in impact design, sheet metal process design and system identification are used to demonstrate the method. The methodolo- gy has been incorporated as a parallel solver in the commercial software code LS-OPT.
U. Schramm, H. Thomas, K. Hayes – Altair Engineering Inc., Troy, MI
In the automotive industry the crashworthiness of a design is of special interest. Non-linear finite element analysis, such as in LS-DYNA, is applied to predict the structural responses. Conclusions from these computations can lead to significant design modifications. Usually, intuition leads the iterative process of finding the best design. It is often hard to determine these design modification from the analysis results. In some cases many variations are tried before a satisfactory design is found . Structural optimization and Design of Experiments Studies based on computational methods are useful tools to support the process of finding the right design. The complexity of the layout can be described mathematically as an optimization problem. Using the results of a computational optimization, the decision process can be improved. Optimization of structural elements can lead to significant cost reductions within the design process itself, or with regard to the final design. Industrial application of structural optimization depends on the availability of software products. For linear statics and dynamics such software is available and fairly well supported. Layout and shape optimization can be performed to design structural parts. In design considering crashworthiness no algorithms are available to perform sensitivity analysis and optimization as known in linear statics. An alternative approach is to use response surface methods in conjunction with such a code. Also, DOE approaches can be used.
Jeffrey G. Zais – IBM
The MPI version of LS-DYNA includes several options for decomposition of the finite element model. In this paper, the use of these options will be explored, for both metalforming and automotive crash simulations for input decks with size ranging from small to very large. The effect on elapsed time performance and scalability will be measured for different partitioning options. In addition, performance characteristics of a workstation cluster will be evaluated.
Bhavik R. Shah, Richard M. Sturt – Ove Arup & Partners,, Aram Kasparian – Arup
This paper describes the use of LS-DYNA for pedestrian protection analysis. A testing procedure has been documented, that may form the basis of proposed future legislation in Europe. Testing is already carried out regularly as part of the European New Car Assessment Program. Large-scale changes in current styling and engineering practices are needed to pass the tests; often, such changes can be accommodated only if identified at concept or pre-concept stage. This paper includes validation of the impacter device models and illustration of their use in establishing design concept guidelines at a non-product-specific level. The limitations imposed on styling are potentially onerous, and are discussed in the paper.
Brian A. Coon, Phanidhar Anugonda, John D. Reid – University of Nebraska-Lincoln
An LS-DYNA finite element model was developed to analyze the structural behavior of an aluminum beverage can subjected to a piercing load applied to the sidewall of the can. Physical testing was performed to help verify the simulation accuracy. The piercing was intended to simulate the damage to a can that might occur during the manufacturing process. Impacts of 5 m/s and 10 m/s were performed with both blunt (flat) and sharp (45 tip) steel rods. It was found that separated elements with tied nodal constraints more accurately represent the behavior of the can subjected to a piercing load than merged element nodes. It was also found that the more crushing a can undergoes before piercing occurs, the more energy the can material absorbs. However, there is an upper limit to the crushing based on the speed and shape of the impactor.
Joe Hassan – DaimlerChrysler, Peter Schuster, G. Frederick – Ford Motor Company
Modeling of foams has become a very important task for automobile engineers due to the fact that compressible plastic foams are used throughout the interior and bumper systems of modern automobiles for safety enhancement and damage prevention. To date, most work has focused on predicting foam performance up to approximately 80% compression. However, in certain cases, it is important to predict the foam under maximum compression, or ‘bottoming- out.’ This paper uses one such case—a thin low-density bumper foam impacted by a pedestrian leg-form at 11.1 m/s—to investigate the ‘bottoming-out’ phenomenon. Multiple material models in three different explicit Finite Element Method (FEM) packages (RADIOSS, FCRASH, and LS-DYNA) were used to predict the performance. The finite element models consisted of a foam covered leg-form impacting a fixed bumper beam with a foam energy absorber. The predicted leg-form acceleration over time was then compared to the leg-form acceleration observed during a physical test. Within the finite element models solid elements using material types such as honeycomb, advanced foam curvilinear recoverable, strain rate foam recoverable, and low density foam were evaluated as to their accuracy in simulating ConforTM foam on the pedestrian leg-form and polyurethane energy-absorbing foam on a bumper beam under extreme compression or deformation conditions. Extreme deformation which occurs after 80% compression can cause excessive hourglassing of certain types of elements. During this extreme event many solid element material types will not exhibit the correct foam behavior, consequently the results lead to an incorrect prediction. This study attempts to determine the best material type to use during this type of large deformation impact.
Jason R. Smith, Lawrence C. Bank, Michael E. Plesha – University of Wisconsin-Madison
LS-DYNA 940.2 was used to study the response of composite box beams subjected to oblique (or inclined) impacts by a rigid cylinder. The square cross-section composite beams were 1000 mm long with 50 mm by 50 mm nominal cross-sectional dimensions. The rigid cylinder had a 50 mm diameter and a 100 mm length and impacted the box beam on the top panel. The composite box beam and the cylinder were modeled with 3 mm thick Belytschko- Tsay shell elements. Material 54: MAT_ENHANCED_COMPOSITE_DAMAGE was used to model the orthotropic composite material used in the sidewalls of the box beam. In order to simulate an experimentally observed progressive “tearing” failure in the box beams during the impact events, spotwelds were used to model the corners of the beams (i.e. the joints between the four sides of the box beam). Spotweld failure parameters were calculated from the transverse tensile and in-plane shear strengths of the composite material. The benchmark analysis used for the study was one in which the rigid cylinder hit the beam at an incident angle of 25° to the horizontal axis at a velocity of 2 m/s. The coefficient of friction between the cylinder and the beam was 0.1. The results of the benchmark analysis were compared to results of analyses with various angles of impact, impact velocities, and coefficients of friction. Results were compared with respect to the displacement path of the cylinder, the angle of the path of the cylinder with respect to the horizontal direction (rebound angle), the change in velocity of the cylinder, and the resultant impact force on the cylinder. In general, the rebound angle and velocity of the cylinder appeared to have a rational dependence on the incident angle, the coefficient of friction, and the initial velocity.
Roger Chu, Guangye Li – SGI
In parallel computation, the scalability of the application software is critical. It is especially important when large number of processors are used. In this paper, we present the scalability results of LS-DYNA on the SGI multiprocessor computer systems. Furthermore, since MPP- DYNA is a domain decomposition based software, data partitioning algorithms play an important role in the scalability of the code. We will show in this paper that for some car crash models, special data partitioning techniques may improve the scalability significantly.
Youn-Seo Roh – Sun Microsystems, Inc.
With LS-DYNA MPP, scalable SolarisTM operating system and the MPI library, Sun Microsystems’ StarfireTM server proved to be capable of producing a scalable solution for large-scale automotive crash simulation problems. It was found that a proper decomposition plays a significant role in achieving optimal scaling results for large-model, computation- intensive runs. Also, a large amount of external cache memory on the Starfire SMP server was found to be crucial for optimal runtime performance. With proper decomposition, a Starfire server was able to achieve 30X speedup and 93% efficiency with 32 processors in the simulation run of the NCAC Neon model consisting of 270,000 elements. Version 940.2a of LS-DYNA MPP showed good repeatability over largely different numbers of processes. It also displayed an exact repeatability on different runs when the command setting and number of processes are kept constant.
Alex Akkerman , Ravi Thyagarajan – Ford Motor Company,, Mike Burger, Nielen Stander – Livermore Software Technology Corp.,, Bob Kuhn, Hrabri Rajic – Kuck & Associates, Inc.
The ability to quickly design new vehicles with optimal crashworthiness is a goal of automotive manufacturers. This paper takes steps towards that goal by automating manual design iterations. The crashworthiness of an instrument panel was enhanced using LS-OPT and LS-DYNA. It is shown that: • LS-OPT can modify the shape of non-styled parts in the instrument panel in order to • The design was generated several times faster than with manual methods. LS-OPT • The dramatic increase in the size of the design space caused by shape optimization • The cost of obtaining these designs can be reduced by using distributed computing to enhance its crashworthiness by using a parametric preprocessor, e.g. TrueGrid®. generated and executed LS-DYNA runs without need for manual result analysis. was managed efficiently by LS-OPT. explore the design space on workstations which would otherwise be underutilized.
Robert W. Bielenberg – University of Nebraska-Lincoln, Scott H. Magner – University of Nebraska-Lincoln, John D. Reid – University of Nebraska-Lincoln
Previous research has demonstrated that finite element analysis can be used to predict the structural behavior of aluminum beverage cans including the buckling of the sidewall of the can. Buckling of a beverage container can occur when the lid is pressed on dented cans during assembly. The purpose of this research was to simulate the sidewall indentation and the buckling of aluminum cans with a deformed sidewall using LS-DYNA and validate the results through physical testing. Simulation of the sidewall indentation was done with an impacting sphere. Parameters investigated through simulation included the size of the impacting sphere, velocity of sphere, and impact height along sidewall of can. Results from this study are maximum and final can deflection, maximum and final energy absorbed by the can, and force deflection data. Simulation of the buckling of the deformed can was also performed. Results from the deformed can buckling model compared well with physical testing based on buckled geometry, buckling load, and external work to buckle. The deformed can model proved capable of accurately simulating the buckling of the deformed can.
Eann A. Patterson, Chris J. Carmody, Ian C. Howard – The University of Sheffield
The motions of natural and replacement valve leaflets are complex functions of a large number of interactions. The principle concern of the simulation work is the investigation of how natural valves operate whilst attached to a deformable aorta close to its connection with the left ventricle. This involves the interaction of a fluid flow with soft, highly deformable structures. LS-DYNA was used to analyse the system using a series of models with fluid- solid interaction. A ventricle model helped create a detailed prediction of the temporal and spatial variation of flow into the aorta as the ventricle contracts. The principle input to this model was experimental data on displacements. This allowed a flow pattern to emerge naturally in the ventricle. This flow pattern was then available for input into the aortic valve model. The creation of this was a significantly non-trivial task. There are several aspects whose computational demands can be mutually destructive without care in the modelling. These include the effects of contact, spatially moving flow gradients, and the large deformations of the aortic wall and the sinuses. The development of the aortic valve model used linear elastic properties for the different solid materials. Subsequently the simulation progressed to using fully non-linear properties. The paper highlights some of the difficulties encountered and the solutions found, as well presenting some of the results.
R. Boyd – Altair Engineering Ltd, R. Royles – University of Edinburgh, K. M. M. El-Deeb – Linear & Non-linear Structural Dynamics Ltd
Numerical modelling of underwater explosion (UNDEX) loading using LS-DYNA was studied in free field conditions and in relation to an axisymmetric thin shell of revolution – an echinodome in a floating submerged and tethered configuration. The formulation utilised was multi-material arbitrary Lagrangian Eulerian. Based on preliminary modelling, backed by existing data, numerically reproducible experiments were designed for validation purposes. The mesh generation and experimental validation are described and compared.
Fei-chin Jan, Oladipo Onipede Jr. – University of Pittsburgh
This project uses LS-DYNA to simulate the rolling deformation of a flat steel sheet into a panel of particular shape. The process involves the gradual deformation of the steel sheet by passing it through a series of rollers at a constant speed. Each of these sets of rollers is oriented at a slightly different angle to incrementally increase the deformation of the sheet until the desired geometry is obtained in the panel. Since the sheet could be going through several different sets of rollers at the same time, the deformation process is very complex and highly non-linear. During this process, the sheet metal panel undergoes plastic deformation and develops residual stresses. Some of the problems encountered with these panels include localized buckling, undesirable local deformation at the front (head) of the panel and excessive spring back of the end of the panel (tail). These problems are also observed in the results from the simulation and methods to minimize their effect are investigated. Other issues encountered in the simulation include the contact mechanism between the moving panel and a moving roller, effect of roller size and placement, panel thickness, panel speed and roller friction. An adaptive mesh was used to efficiently mesh the plate and rollers at critical locations. The results obtained should help improve both the simulation process and the actual cold-roll-forming-process especially when new or different metals are being introduced.
Waheed Uddin – The University of Mississippi
Nondestructive evaluation of highway and airport pavements is performed by deflection testing, such as a falling weight deflectometer (FWD). Many agencies use FWD deflection data to backcalculate pavement moduli using subjective inputs and forcing the moduli within a pre-selected range for each material. The failure of many pavement projects can be attributed to the uncertainties in these material inputs. The use of static elastic layered analysis and two- dimensional static finite element analysis programs is inadequate to calculate pavement responses and to relate these to pavement performance. This paper presents some results of advanced three dimensional-finite element (3D-FE) computer simulations carried out on selected pavement-subgrade models of asphalt pavements, subjected to a standard FWD impact load. Good agreement is shown between simulated and measured FWD deflections. Examples of nonlinear FWD moduli for an aircraft wheel load are presented. Effects of viscoelastic material properties on pavement responses to dynamic FWD loading are discussed. The LS- DYNA contact surface definitions are applied for dynamic analysis of pavements. The paper demonstrates the use of advanced finite element dynamic analysis procedures for correctly simulating pavements subjected to dynamic loads produced by nondestructive evaluation equipment and dynamic wheel loads.
Tuhin Halder – Lear Corporation
Latches play an increasingly vital role in an automotive seat system due to the recent introduction of the mandatory 3-point restraint system for center occupants. Traditionally, latches were designed to carry the seat back load, the head restraint load, and the luggage intrusion load. For the new Seat Integrated Restraint (SIR) systems, latches have to meet a very high load requirement with a very low range of allowable displacement. Hence, a latch has to meet its basic function, which is to fold and tumble, and it has to pass this stringent non-linear loading condition. Finite Element Analysis (FEA) has been widely used to simulate latches on a component level. With the introduction of the displacement requirement limitation for the SIR retractor, component level analysis is redundant. The paper discusses an efficient new method to simulate the seat system along with latches that yield meaningful results and a consistent level of correlation.
Jean Luc LACOME – DYNALIS
A new particle element has been added to LS-DYNA. It is based on Smoothed Particle Hydrodynamics theory. SPH is a meshless lagrangian numerical technique used to model the fluid equations of motion. SPH has proved to be useful in certain class of problems where large mesh distortions occur such as high velocity impact, crash simulations or compressible fluid dynamics. First, we introduce the basis principles of the SPH method. Then the coupling of this technique to LS-DYNA is presented and the input needed for such analysis is provided.
Oladipo Onipede, Carlos J. Gomes – University of Pittsburgh
This paper presents the finite element analysis and results of springback in a U-shape cross section made of high strength anisotropic steel. The results are compared with those obtained from two isotropic materials that have the same yield stresses as those of the principal directions of the anisotropic steel sheet. The principal directions are the directions of the sheet that have the largest and smallest yield stresses respectively. The results show the discrepancy between springback predicted by the isotropic and anisotropic materials, but also the variability of springback with respect to the angle of orientation of the anisotropic steel sheet. This may help address the question of when it is appropriate to use isotropic material properties for anisotropic materials when it comes to predicting springback.
Zhongqin Lin, Gang Liu, Weili Xu, Youxia Bao – Shanghai Jiaotong University
Accurate prediction of springback is the precondition of controlling the springback. The precision of springback prediction is affected by many parameters in both forming process and springback process. The 2-D draw bending benchmark of NUMISHEET’93 is used as an example to investigate the influencing of numerical parameters in LS-DYNA and LS-NIKE3D, which includes solution approach, dynamic effect, number of the dies’ corner elements and blank element size on the springback simulation. Comparing the simulation results with experimental results, some basic principles have been given for springback simulation.
Robert F. Lucas – Lawrence Berkeley National Laboratory
Brian Cowell, Anthony Kellicut, Adam Fisher – Tower Automotive
This paper describes the effects of forming simulation results on crash and durability performance and the impact of the method of transferring results from one simulation to the next. Forming simulation may not always result in a mesh that is ideally suited for static or crash analysis. Tower Automotive has developed software to map forming simulation results from the formed mesh to an entirely different LS-DYNA or NASTRAN mesh of the same part. Simulations of part fabrication represent both hydroforming and mechanical forming. Static simulation is performed in NASTRAN using the work-hardened state as the material input for each element. Other formed parts are subjected to a representative crush load. The effect of transferring results on the same mesh and mapped onto a dissimilar mesh is compared. Results of several crush simulations will be shown, including with forming results, without forming results, and forming results mapped onto a different mesh.
Mark A. Christon – Livermore Software Technology Corp.
Over the past year, efforts have been underway to extend LS-DYNA’s extensive list of capabilities to include an incompressible CFD solver. The focus of this paper is on the second-order approximate projection method used in LS-DYNA to solve the time-dependent Navier-Stokes equations. In order to address the computational demands of the implicit pressure field, LS-DYNA relies, in part, upon an A-conjugate projection technique coupled with the preconditioned conjugate gradient method and sub-domain preconditioners. Results of time-dependent laminar and large-eddy simulations are used to illustrate the effectiveness of the projection-based preconditioned conjugate gradient method coupled with the second- order approximate projection flow solver. As a new physics option in LS-DYNA, the incompressible flow solver complements the existing compressible fluid/ALE simulation capabilities.
Saiphon Charoenphan, Lawrence C. Bank, Michael E. Plesha – University of Wisconsin-Madison
In order to obtain the desired coupling between deformation modes that can occur in composite material plates having unbalanced and/or unsymmetric lamination schemes, the appropriate shell element formulation must be selected from the available formulations in LS- DYNA. An investigative study was conducted to determine which of the shell element formulations in LS-DYNA 950 can be used for modeling such plates prior to performing in- depth studies on the behavior of more complex composite material structures. Unbalanced/symmetric and balanced/unsymmetric lamination schemes were studied for single-element and four-element “patch” tests. The elastic response of these models to in- plane tensile loads and out-of-plane bending loading was investigated. The shell elements were used with material model 54 (MAT_ENHANCED_COMPOSITE_DAMAGE). The study focused on determining which of the shell element formulations would produce the expected coupling between deformation modes. The Belytschko-Leviathan shell formulation was found to be the best choice for coupled elastic response. Progressive failures of laminates under in-plane tensile and compressive loads were also investigated using this element formulation.
Jin Wu – University of Cincinnati
Ala Tabiei Director CENTER OF EXCELLENCE IN DYNA3D ANALYSIS Department of Aerospace Eng. & Eng. Mechanics University of Cincinnati The subject of this investigation is the development of an accurate simulation of a truck impacting a strong-post w-beam guardrail system, the most common system in the USA. Detailed methods for system simulation are proposed and three major issues, which involve the use of springs to simulate component crashworthiness behavior, are investigated. Rail to blockout bolt connection, soil-post-dynamic interaction, and effect of ends of guardrail are modeled and simulated. Soil-post interaction is modeled using both Lagrangian and Eulerian meshes and the results using the two methods are presented. Both qualitative and quantitative validation of the crash simulation is presented and discussed. The present paper provides a roadmap for simulation of highway safety structures.
G. S. Choi, H. K. Min – Kia Motors Technical Center
The reason manufacturers invest their time and money in order to improve the performance of dynamic characteristics, fatigue stiffness, NVH and crash safety during the process of vehicle development is directly linked to their competitiveness. Due to the rapid development of the computer CPU and application software, it is possible to perform dynamics analysis and durability design using CAE tools before making a prototype vehicle to reduced time and money in testing and developing a vehicle.
Arthur Tang, Nasser Tamini, David Yang – Engineering Technology Associates, Inc.
The Virtual Proving Ground approach has been developed for simulation of dynamic nonlinear events as applied to automotive durability, ride & handling and noise/vibration/harshness applications. This finite element analysis technique provides a unique method to create and analyze vehicle system models, capable of including vehicle suspensions, powertrains and body structures in a single simulation. Through the development of this methodology, event-based simulations of the vehicle performance, over a given three-dimensional road surface can be performed. The development of methodologies and approaches for performing this type of analysis will be discussed, which make up a “Virtual Proving Ground” environment. Case studies will be presented to show the application of this methodology to a full vehicle system for vehicle durability, ride & handling and noise/vibration/harshness applications. The results of this case study will highlight the potential applications of this approach, as well as the challenges associated with the method.
David W. Nicholson – University of Central Florida, Orlando,, Ricardo F. Moraes – Major of the Army of Brazil, Eduardo Divo, Brian Cahill – Dual Incorporated
A prototype of low cost system is described for visualization of realistic weapons effects experienced by targets undergoing blast and impact, to be used in training of personnel for livefire environments. The system is based on integrating two tools: (a) The Finite Element (FE) impact code LS-DYNA (b) A Virtual Reality Visualization (VRV) system The VRV system was recently developed by DUAL Incorporated of Lake Mary, FL in partnership with the University of Central Florida (UCF). It consists of a PC- level graphics workstation, a head mounted display, motion trackers, a multi-degree of freedom mouse, drivers and a software toolkit, all of which have been established at DUAL and UCF.